This bulletin applies to 2006-2015 Chevy Corvette, 2007-2013 Avalanche, 2007-2016 Silverado/Suburban/Tahoe, 2015-2016 Colorado, 2010-2015 Camaro, 2010-2016 Express, 2011-2016 Caprice and 2014-2016 Chevy SS vehicles, all equipped with 6L45, 6L50, 6L80 or 6L90 automatic transmissions (RPO MYS, MYB, MYC, MYD). Vehicles may experience no reverse and no second gear after upper valve body replacement. RPO stands for regular production option. A vehicle’s RPO label should be found on the driver door label, on the glove box door or trunk floor, depending on the vehicle.
In some cases, the input speed sensor (ISS) signal and the output speed sensor (OSS) signal may be missing. This condition may be caused by the installation of the incorrect upper valve body.
Upper valve bodies are unique by transmission RPO. Each upper valve body has four posts, labeled A, B, C and D on the top side of the upper valve body. Inspect the upper valve body to determine the correct RPO usage.
The post corresponding to the correct RPO will be milled off of the casting. If the A post is milled, this indicates MYA. If the B post is milled this indicates MYB, etc. The oil passage holes that feed the center support and low and reverse clutch and 2-6 clutch contained within the center support vary by transmission and corresponding upper valve body. The ISS and OSS mounting locations also vary by transmission. The incorrect upper valve body does not properly locate the oil feed holes and speed sensors.
In this example, the “C” post has been milled off, indicating an application for RPO MYC.
Transmission versions feature different locations for the oil feed holes and sensor locations.